I get the point and I'm ok with the fact that Tribunals should not be at war with other cabal besides Entropy and Outlanders.

My question is: why keep using a game mechanic (wich has been exploited few times before) that puts Tribunal players at disadvantage when other players decide to use it for PK reasons? A Spire Immortal leader policy (severely punished if not observed) that forbidden war on other cabals could be used instead, no?

There's a big difference between the very 'unbalanced' abilities you mentioned and the situation i'm talking about: players can choose to become criminal -and suffer the unbalanced consequence - while Tribunal players have no say in the choice of being put at disadvantage.